1. Field of the Invention
The present invention generally relates to heat exchanger tube repair apparatus using a sleeve to repair an inaccessible tube section and more particularly to such tube repairs requiring sleeve end expansion apparatus.
2. Description of the Prior Art
Repair sleeving is known to repair defective portions of heat exchanger tubes. In this defective portion of the tube, both ends of the repair sleeve can be expanded into the parent tube by roll expansion, hydraulic expansion, or other expansion methods. For repair sleeving used to repair heat exchangers that contain soft tubing, such as brass, copper-nickel, copper, carbon steel, etc., there is a need to expand the ends of the sleeve into the tube to minimize the risk of flow erosion/corrosion in the parent tube. This expansion operation minimizes the internal diameter (ID) step between the sleeve and the tube. Another method used to minimize the ID step is to press fit very thin repair sleeves into the defective tube portion. However, if a sleeve is to be installed deep into the tube bundle it is not practical to insert a press fit sleeve due to possible tube ID restrictions. Another option to get the sleeve into close contact with the tube ID is to roll expand the ends. However, it is not always practical to roll expand the sleeve ends due to multiple sleeve locations along the tube length and due to tooling access issues around the heat exchanger. In some instances, the repair sleeve end may be located up to 50 ft. from the tube inlet end but there may be only 5 ft. of clearance between the tube end and an obstruction.
Other than roll expansion of sleeve ends or the use of a special thin sleeve design, no other methods of expanding the very end of the sleeve into contact with the tube are known. Various methods have been tried, including the use of an ID pressurized bladder to expand the sleeve end, but none have met the criteria of producing a reliable sleeve end expansion to a failed tube area located deep within a tube.
The previously explained known sleeve repair techniques used in easily accessible tube areas are discussed in the following U.S. Patents.
U.S. Pat. No. 5,008,996 teaches the use of expansion sleeves in failing areas of heat exchanger tubes. However, it fails to recognize any solution for eliminating the step problem at the end of the sleeve in soft metal heat exchanger tubes and teaches the expansion of sleeves using known rolling and welding techniques.
U.S. Pat. No. 4,876,871 also teaches the use of expansion sleeves in failing areas of heat exchanger tubes. However, it also fails to recognize any solution to the step problem at the end of the sleeve in soft metal heat exchanger tubes and teaches the expansion of sleeves using known rolling devices for sleeve expansion.
U.S. Pat. No. 4,829,648 teaches the use of expansion sleeves in failing areas of heat exchanger tubes. However, it again fails to recognize any solution to the step problem at the end of the sleeve in soft metal heat exchanger tubes and teaches the use of a mandrel to expand the sleeve into the tube.
In view of the foregoing it will be seen that while the use of expansion sleeves in failing areas of heat exchanger tubes are well known, the step problem at the end of the sleeve in soft metal heat exchanger tubes, with the repair sleeves in inaccessible areas, is not specifically addressed in the known prior art and there is no teaching of how to reach such inaccessible areas of the tube let alone how to eliminate the step problem in repair sleeves.
The present invention solves the mentioned problems associated with known sleeving tube repairs and others by disclosing a method and apparatus for minimizing the step between the inside diameter of a soft metal heat exchanger tube and a sleeve used to repair a failing section of the tube where the known devices used for sleeve end roll expansion cannot reach.
To accomplish this task, a compression bladder tool is used to expand the end of such inaccessible heat exchanger sleeves. The expansion is performed by locating a plastic bladder inside the sleeve at one end and hydraulically compressing the plastic bladder. As the bladder is compressed in length it expands as a function of Poisson""s ratio, expanding the sleeve end in the process. The hydraulic expansion force can be varied to produce the appropriate sleeve end expansion to thus minimize the step between the tube section and the repair sleeve. The bladder device is then moved to the other end of the repair sleeve and the process repeated.
In view of the foregoing it will be seen that one aspect of the present invention is to provide a compressible bladder tool for expanding repair sleeve ends in inaccessible failed tube sections.
Another aspect of the present invention is to provide a compressible bladder tool for expanding repair sleeve ends in inaccessible failed tube sections.
Yet another aspect of the present invention is to provide a hydraulically actuated bladder tool for expanding repair sleeve ends into tubes using an easily controlled sleeve end expansion process.
These and other aspects of the present invention will be more fully understood after consideration of the following description of the preferred embodiment taken in conjunction with the accompanying drawings.